Bug 1837185 - Use realistic loader in test_webext_apis.js + fix failures...

Bug 1837185 - Use realistic loader in test_webext_apis.js + fix failures r=devtools-reviewers,jdescottes, a=dmeehan

listAddons was broken because webbrowser.js imported AddonManager
through the wrong loader. Consequently, a new instance of the
AddonManager module was loaded, instead of the alreaady-initialized one
from the browser. This lead to the observed bug in the report.

test_webext_apis.js was not realistic because it did not use a dedicated
loader like DevToolsStartup. That prevented the test from catching the
regression. This patch fixes that by replicating the logic at
https://searchfox.org/mozilla-central/rev/aec3a901e6f6b3041b5ec457c9111a042cef1fb1/devtools/startup/DevToolsStartup.sys.mjs#1075-1101

Differential Revision: https://phabricator.services.mozilla.com/D180253

devtools/server/actors/addon/addons.js

@@ -10,7 +10,8 @@ const {
 } = require("resource://devtools/shared/specs/addon/addons.js");
 
 const { AddonManager } = ChromeUtils.importESModule(
-  "resource://gre/modules/AddonManager.sys.mjs"
+  "resource://gre/modules/AddonManager.sys.mjs",
+  { loadInDevToolsLoader: false }
 );
 const { FileUtils } = ChromeUtils.importESModule(
   "resource://gre/modules/FileUtils.sys.mjs"

devtools/server/actors/webbrowser.js

@@ -49,8 +49,11 @@ loader.lazyRequireGetter(
   true
 );
 const lazy = {};
-ChromeUtils.defineESModuleGetters(lazy, {
-  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+loader.lazyGetter(lazy, "AddonManager", () => {
+  return ChromeUtils.importESModule(
+    "resource://gre/modules/AddonManager.sys.mjs",
+    { loadInDevToolsLoader: false }
+  ).AddonManager;
 });
 
 /**

devtools/server/tests/xpcshell/head_dbg.js

@@ -76,6 +76,31 @@ const systemPrincipal = Cc["@mozilla.org/systemprincipal;1"].createInstance(
 
 var { loadSubScript, loadSubScriptWithOptions } = Services.scriptloader;
 
+/**
+ * The logic here must resemble the logic of --start-debugger-server as closely
+ * as possible. DevToolsStartup.sys.mjs uses a distinct loader that results in
+ * the existence of two isolated module namespaces. In practice, this can cause
+ * bugs such as bug 1837185.
+ */
+function getDistinctDevToolsServer() {
+  const {
+    useDistinctSystemPrincipalLoader,
+    releaseDistinctSystemPrincipalLoader,
+  } = ChromeUtils.importESModule(
+    "resource://devtools/shared/loader/DistinctSystemPrincipalLoader.sys.mjs"
+  );
+  const requester = {};
+  const distinctLoader = useDistinctSystemPrincipalLoader(requester);
+  registerCleanupFunction(() => {
+    releaseDistinctSystemPrincipalLoader(requester);
+  });
+
+  const { DevToolsServer: DistinctDevToolsServer } = distinctLoader.require(
+    "resource://devtools/server/devtools-server.js"
+  );
+  return DistinctDevToolsServer;
+}
+
 /**
  * Initializes any test that needs to work with add-ons.
  *

devtools/server/tests/xpcshell/test_webext_apis.js

@@ -10,11 +10,10 @@ const { ExtensionTestUtils } = ChromeUtils.importESModule(
   "resource://testing-common/ExtensionXPCShellUtils.sys.mjs"
 );
 
+const DistinctDevToolsServer = getDistinctDevToolsServer();
 ExtensionTestUtils.init(this);
 
-// The `AddonsManager` test helper can only be called once per test script.
-// This `setup` task will run first.
-add_task(async function setup() {
+add_setup(async () => {
   Services.prefs.setBoolPref("extensions.blocklist.enabled", false);
   await startupAddonsManager();
 });
@@ -44,10 +43,10 @@ async function sendRequest(transport, request) {
 // If this test case fails, please reach out to webext peers because
 // https://github.com/mozilla/web-ext relies on the APIs tested here.
 add_task(async function test_webext_run_apis() {
-  DevToolsServer.init();
-  DevToolsServer.registerAllActors();
+  DistinctDevToolsServer.init();
+  DistinctDevToolsServer.registerAllActors();
 
-  const transport = DevToolsServer.connectPipe();
+  const transport = DistinctDevToolsServer.connectPipe();
 
   // After calling connectPipe, the root actor will be created on the server
   // and a packet will be emitted after a tick. Wait for the initial packet.